Influence of energy levels on the electronic properties of organic light harvesting devices

Abstract The charge carrier generation efficiency and the charge transfer rate at the interface between charge carrier generation layer (CGL) and charge transport layer (CTL) were determined in dependence of the energy gap between the highest occupied molecule orbital (HOMO) levels. The bilayer photoreceptors were characterized by the steady-state photoconduction method. The investigated photoreceptors contained 4,4′-[(2,5-di-phenyl-1,3,4-oxadiazol)-bis(azo)]-bis[3-hydroxy-(2H-benzimidazo[2,1- a ]benz[ d , e ]isoquinolin-7-one)] as CGL. The energy gap between CGL and CTL was varied by employing seven different triphenylenediamine derivatives (TPDs). The charge carrier generation efficiency and charge transfer rate measured were plotted against the energy gap. The result could be explained by the Marcus theory for energy gaps larger than 0.65 eV.